1. Field of the Invention
The present invention relates generally to regenerative thermal oxidizer systems for waste gases containing volatile hydrocarbons. More particularly, the invention relates to flow-control dampers for routing of process and purge gas flow through inlet, outlet and idle regenerators.
2. Description of the Prior Art
Regenerative thermal oxidizer systems for pollution reduction employ control of the process gas flow path through multiple regenerative beds to increase efficiency in oxidizing the volatile hydrocarbon contaminants present in the process gas, while reducing the overall requirement for additional fuel input to raise gas temperature to create oxidation. Gas flowing from the process is routed through a first regenerator bed which heats the gas prior to entering a combustion chamber. Complete oxidation of the gas occurs in the combustion chamber and the purified gas is then routed through a second regenerator bed which cools the gas and heats the regenerator bed prior to exhausting of the gas to the atmosphere. Reversal of the process by providing the inlet process gas to the regenerator which has been heated by the purified outlet gas allows effective use of the reclaimed heat energy. Typical regenerator systems operate with three or more regenerator beds allowing an idle regenerator which has previously been used as an inlet for the process gas to be purged of any remaining contaminants in the bed prior to reversing flow through the bed for use as an outlet regenerator. Numerous configurations for such systems are disclosed in the prior art. However, exemplary systems in which the present invention may be employed are disclosed in U.S. Pat. Nos. 5,098,286 and 5,026,277, entitled Regenerative Thermal Incinerator Apparatus having a common assignee with the present application.
Control dampers for thermal regenerative systems, such as the prior art described, typically employ a single butterfly or gate arrangement on each individual inlet and outlet duct connected to the regenerators in the oxidizer system. Such systems typically require six dampers for the inlet and outlet ducts of a three regenerator system with an additional three dampers located in purge ducts connected to the regenerators. Each damper requires individual control and meeting the requirements of the process flow entails coordination of operation of all valves individually to avoid flow disruption.
It is therefore desirable to reduce the number of control elements required in the flow control system and the number of dampers to reduce the number of moving parts required in a high thermal stress environment.